It is generally understood in sewing machines that the timing between the reciprocating needle and the rotating loop taker or hook is critical so that the loop seizing beak of the hook will be in the proper position for seizing a loop of thread from the needle for preventing skip stitches or the like. The loop seizing beak of the hook must pass closely adjacent to the needle to seize the loop of thread therefrom and must pass the needle in timed relation thereto and at a fixed distance beneath the work supporting surface of the machine. It has been necessary heretofore to provide separate means for making final adjustment of the hook point to needle relationship which means have been cumbersome and difficult to adjust. Further, in machines wherein the hook is driven by gearing between the machine drive or bed shaft and the hook shaft the meshing and timing of this gearing also becomes critical.
It has been proposed that to account for the critical relationship between the hook loop seizing beak and the needle means be provided for adjusting their relative positions. For example, such means are disclosed in U.S. Pat. No. 3,362,364, Japanese Utility Model Registration No. 581,203, Jan. 26, 1963, or East German Patent No. 100,036, Sept. 5, 1973. However, devices as disclosed in the aforementioned patents have not always proved satisfactory since in cases wherein there is a gear drive between the drive shaft and the hook shaft, when such adjustments are made the meshing and timing of these gears is often disturbed.
According to the present invention, means are provided for permitting adjustment between the hook beak and the needle without disturbing the meshing and timing of the drive gears between the drive shaft or bed shaft and the drive gear connected to the hook shaft.
The construction of the present invention provides for a first bevel gear fixed to the bed shaft of the sewing machine which meshes with a second bevel gear or driven bevel gear which is freely rotatable on the outside diameter of the bushing supporting the hook shaft. An interposer member is fastened to the hook shaft and is connected in driving relationship with the driven bevel gear by means of a driver member. The hook shaft is disposed in a bore in a hook shaft bushing which bore has its axis eccentric to or spaced from the true axis from which the outer peripheral surface of the bushing is generated. The interposer member is disposed co-axially with the axis of the hook shaft. In order to provide adjustment between the loop seizing beak of the hook, means may be provided for rotating the hook shaft bushing member which, as described above, has a bore whose axis is eccentric to the true axis of the bushing itself so that as the bushing is rotated the hook shaft will be radially displaced which in turn changes the position of the beak of the hook. Since the interposer member is co-axial with the hook shaft rotation of the hook shaft bushing about its axis will radially displace the interposer but because of the driving relationship between the interposer and the driven bevel gear, this displacement does not affect the relative position of the driven bevel gear and therefore will not affect its meshing engagement with the bevel gear on the bed shaft or the timing of the drive for the hook.
Accordingly, it is one object of the invention to provide a novel and improved drive mechanism for a rotary hook.
It is another object of the invention to provide a novel and improved means for adjusting the relative position of the loop seizing beak of the rotary hook relative to the needle which adjustment does not affect the meshing and timing of the gear drive for the rotary hook.
Other objects and advantages of the invention will be best understood upon reading the following detailed description with the accompanying drawings.